甲公司与龙某签订一投资合同，约定：双方各出资200万元，设立乙有限责任公司；甲公司以其土地使用权出资，龙某以现金和专利技术出资(双方出资物已经验资)；龙某任董事长兼总经理；公司亏损按出资比例分担。双方拟定的公司章程未对如何承担公司亏损作出规定，其他内容与投资合同内容一致。乙公司经工商登记后，在甲公司用以出资的土地上生产经营，但甲公司未将土地使用权过户到乙公司。
2005年3月，乙公司向丙银行借款 200万元，甲公司以自己名义用上述土地使用权作抵押担保。同年4月，甲公司提出退出乙公司，龙某书面表示同意。2008年8月，法院判决乙公司偿还丙银行上述贷款本息共240万元，并判决甲公司承担连带清偿责任。此时，乙公司已资不抵债，净亏损180万元。另查明，龙某在公司成立后将120万元注册资金转出，替朋友偿还债务。
基于上述情况，丙银行在执行过程中要求甲公司和龙某对乙公司债务承担责任。甲公司认为，自己为担保行为时，土地属乙公司所有，故其抵押行为应无效，且甲公司已于贷款后1个月退出了乙公司，因此，其对240万元贷款本息不应承担责任；另外乙公司注册资金中的120万元被龙某占用，龙某应退出120万元的一半给甲公司。龙某则认为，乙公司成立时甲公司投资不到位，故乙公司成立无效，乙公司的亏损应由甲公司按投资合同约定承担一半。

甲公司认为其已退出乙公司的主张能否成立为什么( )。

A．不能

B．可以

C．股东在公司登记后，不得抽回投资

D．股东随时可以退出公司

About fifty years ago, plant physiologists set out to grow roots by themselves in solutions in laboratory flasks. The scientists found that the nutrition of isolated roots was quite simple. They required sugar and the usual minerals and vitamins. However, they did not require organic nitrogen compounds. These roots got along fine on mineral inorganic nitrogen. Roots are capable of making their own proteins and other organic compounds. These activities by roots require energy, of course. The process of respiration uses sugar to make the high energy compound ATP, which drives the biochemical reactions. Respiration also requires oxygen. Highly active roots require a good deal of oxygen.The study of isolated roots has provided an understanding of the relationship between shoots and roots in intact plants. The leaves of the shoots provide the roots with sugar and vitamins, and the roots provide the shoots with water and minerals. In addition, roots can provide the shoots with organic nitrogen compounds. This comes in handy for the growth of buds in the early spring when leaves are not yet functioning. Once leaves begin photosynthesizing, they produce protein, but only mature leaves can "export" protein to the rest of the plant in the form of amino acids.

The scientists found what the isolated roots need is________.

A．quite natural

B．sugar, minerals and vitamins

C．some rare vitamins

D．organic nitrogen compounds